The present invention relates to a bleed screw cap hydraulic equipment, for example, an air bleed screw provided with a cylinder portion of such as a caliper member in a disc brake, and more particularly to an elastic cap for protecting a plug which is provided for exhausting air contained in the cylinder. Such a bleed screw cap is efficiently utilized for preventing rust, corrosion and fouling of the whole bleed screw.
With respect to a disc brake in a vehicle, when air remains within the cylinder of the caliper member, braking operation is reduced. For this reason, the air bleed screw is provided with the cylinder of the caliper member whereby air contained within the cylinder can be exhausted. Often, the air bleed screw becomes contaminated by mud and dust and the like during driving so that the exhaust hole becomes clogged. The present invention overcomes these deficiencies.
The conventional air bleed screw cap will now be described in detail with reference to FIG. 1.
As shown in FIG. 1, boss 1 protrudes from cylinder C. A needle valve 2 is screwed to the boss 1. A conical portion 4 formed on the end of the valve 2 is pushed against a valve seat 3 in the lower end of the screw hole of the boss 1 so that an exhaust port P of the cylinder is closed. An exhaust tube extends through the needle valve 2 from an exhaust hole 5 to a conical head 8. The exhaust hole 5 is in the minor diameter portion 6 of the lower end of the valve 2.
The needle valve 2 has a hexagonal portion 7, the conical shaped head 8, and a neck portion 9. When the hexagonal portion 7 is loosened with a wrench, the needle valve 2 is loosened and the conical portion 4 is separated from the valve seat 3. The exhaust hole 5 of the needle valve 2 is thus in communication with the exhaust port P of the cylinder C so that air contained within the cylinder C is exhausted.
An elastic cap 10 is fitted on the head 8 of the needle valve stem portion 2 so that an exhaust port 8' of the exhaust tube is protected from contamination by dust, mud, and water. The elastic cap 10, a holding ring 12, and a flexible connecting piece 11 are connected integrally with each other to prevent the elastic cap from becoming separated and lost. Additionally, the holding ring 12 is fixedly secured to the hexagonal portion 7.
As described above, the conventional air bleed screw cap is provided to cover the head 8 of the needle valve stem portion 2, and to protect the head 8 and prevent the exhaust port 8' from clogging. However, the conventional needle valve 2 thus constructed suffers from the following problem. During use, rain water or mud water flows into the engaging portion between the needle valve 2 and the screw hole of the boss 1 resulting in rust, corrosion and contamination, and the hexagonal portion 7 becomes corroded and damaged.